Diagonal filters

[dabreegster]

Parity with old version

[dabreegster]

We should discuss before starting this one

[TFCx]

Is it a very specific case of intersection customization ?

[dabreegster]

In v1, you could click 4 way intersections to toggle:


These are used in the US sometimes. I think they can be helpful for grid layouts, with many 4-ways.

[michaelkirk]

I was unable to apply a diagonal filter in v1. Any hint how/where to achieve this?

no-diagonal-filter.mov.mp4

Also, from that video - I'm not sure what's happening when I click an intersection a second time - different shortcuts are counted ($n possible shortcuts pass this) , but there's no visual indication of what happens between the first and second click on an intersection.

[dabreegster]

You need to first change the filter type to the red "no entry":

Then you can click 4-ways:

In the old version, there was a request to default to the green symbol over the red. They mean exactly the same thing in the tool, but have different connotations when shown in a consultation. Unfortunately only the red "no entry" one reasonably shows the direction of the filter. Unsolved design problem. In the new version we're rotating the entire icon right now, but the green one and bus gates look pretty strange as a result. #66 is about figuring out something nicer to do -- maybe keep the walking/cycling icon always upright, and add some kind of rotated line underneath it (without implying that the line means "prohibited")? Or maybe the diagonal filter deserves its own special icon? Or maybe we don't use a circular maplibre symbol layer for diagonal filters at all, but instead a thin line (figuring out something to do at low zoom)?

[michaelkirk]

Just to log my understanding after looking at the v1 code base and interface:

Filters placed on intersections are handled differently from filters placed mid-segment.

When it's a 4-way intersection, any filter is a Diagonal filter. You can click to toggle between the two possible orientations for the diagonal filter.

When it's a 3-way intersection, you can click to toggle which of the 3 roads is "no access" - the other two roads remain connected.

I'm not sure what happens at the more exciting 5+-way intersections, but I feel like we can punt on that for now anyway.

In v2, so far we have no support for intersection filters, only mid-segment filters.

[dabreegster]

All correct.

When it's a 3-way intersection, you can click to toggle which of the 3 roads is "no access" - the other two roads remain connected.
I'm not sure what happens at the more exciting 5+-way intersections, but I feel like we can punt on that for now anyway.

This is just a shorthand for a normal mid-segment filter on each of the 3 or 5 or however many choices, near the intersection.

Notably in v2, we don't have a geometric concept of an intersection; the thickened road line in maplibre stretches to meet the other one. Simplest approach is just a CircleLayer centered on 4-way intersection points, with something visual to hint that the user could put a special diagonal there. Or if the CircleLayer is weird to always be a fixed radius in pixels as you zoom the map, we generate a polygon with a fixed radius in meters and use a FillLayer.